1. Technical Field
The present invention relates to an optical module and a process for manufacturing thereof.
2. Related Art
Optical modules for coaxial transmission or reception installed in an optical transceiver such as 10 Gb/s small form-factor pluggable (XFP) transceiver and the like are classified to optical modules for telecom (phone-related) applications utilized for communication distance of 10 kilometers (km) to 40 kilometers and optical modules for datacom (data communication) applications utilized for communication distance of 220 meters (m) to 10 km.
Such types of optical modules for coaxial transmission or reception applications are typically disclosed in, for example, Japanese Patent Laid-Open No. H4-243,179 (1992). FIG. 9 is a cross-sectional view, illustrating a configuration of an optical module disclosed in Japanese Patent Laid-Open No. H4-243,179.
As shown in FIG. 9, an optical module 101 disclosed in Japanese Patent Laid-Open No. H4-243,179 includes a receptacle 102 and a glass containing lens 103. One end surface of the glass containing lens 103 is formed in a spherical lens 103a via an optical polishing process or via a molding process, and the other end surface 103b is formed in a flat surface. Such glass containing lens 103 is fixed in the optical connector-insertion hole 104 in the receptacle 102. An optical connector 105 is inserted into optical connector-insertion hole 104 to allow the end surface of the optical connector 105 mating the end surface 103b of the glass containing lens 103. A laser diode (LD) package 106, for example, is fixed to a section in a side of the receptacle 102, which is opposite to the side where the optical connector 105 is inserted, taking the glass containing lens 103 as a reference. Outgoing beam from an LD pellet 107 within the LD package 106 is focused by means of the lens 103a, and is coupled to an optical fiber 108 in the optical connector 105.
An optical reflection loss of, for example, equal to or higher than 27 dB in the synchronous optical Network (SONET) OC-48 is required for the optical module for the telecom application. Thus, it is configured as shown in FIG. 9 that the optical connector 105 mates the glass containing lens 103 to create mutual physical contacts of both elements. The glass containing lens 103 is fixed in the optical connector-insertion hole 104 of the receptacle 102, via an adhesion employing a low-melting glass.
Related prior art documents include:
Japanese Patent Laid-Open No. H4-243,179 (1992);
Japanese Patent Laid-Open No. 2004-37,478;
Japanese Patent Laid-Open No. H10-260,336 (1998);
Japanese Patent Laid-Open No. 2006-323,132;
Japanese Patent Laid-Open No. H11-54,849 (1999); and
U.S. Pat. No. 7,160,039.
In order to reduce the production costs for the receptacle 102 in the configuration of the optical module 101 disclosed in Japanese Patent Laid-Open No. H4-243,179 (1992) (FIG. 9), it is generally desirable to compose the receptacle 102 with a resin. However, if the glass containing lens 103 is fixed to the receptacle 102 with a low-melting glass, the receptacle 102 cannot be composed of a resin, since the melting point of the low-melting glass is around 400 degrees C., and thus the receptacle 102 is required to be composed of a metal or the like.
While an alternative way for fixing the glass containing lens 103 with an adhesive agent instead of the low-melting glass may be considered, the structure described in Japanese Patent Laid-Open No. H4-243,179 may exhibit insufficient bonding strength, due to a difficulty in the injection of or the coating with the adhesive agent. In addition, the optical path length may be disturbed, due to a pollution over the surface of the lens 103a or over the end surface 103b physically contacted with the optical connector 105 with an adhesion of the adhesive agent. It is also pointed out in Japanese Patent Laid-Open No. 2004-37,478 that it is difficult to fix the glass containing lens 103 to the receptacle 102 in the optical module 101 having the structure as described in Japanese Patent Laid-Open No. H4243,179 (FIG. 9).
As described above, it is difficult to allow a lens-containing optically-transmissive member such as the glass containing lens being easily adhered to the receptacle with an adhesive agent.